Metropolitan Police Chief Superintendent John Sutherland was speaking at the Tackling Britain's Gang Culture conference, where people whose lives have been affected by gangs and street crime gathered to discuss the causes of the problems, the impact and possible solutions.
Liz Wickham went along to the event:
Mr Sutherland said he had concerns over sexual exploitation and the absence of positive role models, but said children growing up with violence in the home was the biggest contributor to problems in society.
Mr Sutherland said the problem with gangs is not pertinent to a specific age group, neighbourhood or ethnic background.
"It's a whole-society problem that demands a whole-society solution."
He described the absence of "good fathers" as a critical issue, while the sexual exploitation of women, particularly in gang culture where, the conference heard, young girls are raped and used in initiations, is "a horror story, hidden from view".
Addressing ways of finding solutions to gang-related issues, Mr Sutherland echoed the thoughts of fellow speaker Patrick Regan, founder and chief executive of urban youth charity XLP.
Mr Regan said: "We've got to have the courage of our convictions. Those of us who have a position of influence in society, we've got to speak out and speak up. We've got to do it and mean it until things really change. I feel that passionately."
Addressing the crowd at XLP Urban Training Centre in All Hallows-on-the-Wall church, Mr Sutherland received loud applause when he said religious faith has a place in dealing with the problems caused by gang culture.
"This is not a situation we're going to arrest our way out of.
"Faith matters. There is a place for prayer.
"It's not fashionable to say that but frankly we've not got time for fashion anymore."
Today's conference follows a report in October by the Centre for Social Justice (CSJ) think tank, which said the arrests of more than 200 leaders of London street gangs in the wake of 2011's riots had led to an increase in "chaos, violence and anarchy" in the capital.
It also warned that the removal of the so-called "elders" from the streets has backfired by creating a power vacuum in which younger and more hot-headed members seized control of gangs on a wave of violence.
Drawing on interviews with community leaders and former gang members, it warned of an "escalation" of violence as more junior members - known as "youngers" - vie for status and respect in the absence of the restraining hand of older figures who had imposed a code of behaviour.
The CSJ report also revealed a "startling" increase in the number of girl gang members and a rise in sexual violence within gangs, citing one case in which a 13-year-old girl involved with a gang was being sexually exploited by members and was grooming her own 10-year-old sister for the same purpose.
It recommended "addressing the drivers of gang culture, not just the symptoms", including a new multi-agency Whitehall task force to ensure that as much focus is put on prevention as on enforcement.